Over the years various surgical instruments for joining tissue have been developed. Most instruments have been developed utilizing metal staples for joining the tissue. The metal staples are relatively rigid, have their legs sharpened to readily penetrate the tissue, and once penetrated may then be crimped into a clinched position to hold the tissue together as is well known in the art. Instruments of this type are more fully disclosed and described in U.S. Pat. Nos. 3,080,564, 3,079,606, 2,891,250, 3,589,589, 4,207,898 and 4,351,466.
Generally, the instruments comprise a movable member or jaw and a stationary member or jaw. The movable jaw usually carries the metal staples and the stationary jaw carries an anvil which clinches or bends the legs of the staple that pass through the tissue. In use, the tissue is placed between the jaws, the jaws brought to the appropriate gap and the staples driven through the tissue and clinched to set the staple. A major problem with these instruments is the use of the metal staple. While metal staples provide desired hemostatsis in the joining of the tissue, they remain in the tissue and can disrupt future diagnostic techniques such as x-ray diagnosis, computer axial tomography, nuclear magnetic resonance, and the like. To eliminate this problem, it has been found desirable to develop instruments which can set non-metallic fasteners. These are fasteners made from biologically absorbable or non-absorbable polymeric materials. Examples of the absorbable polymeric materials would be the polymers and copolymers of glycolide, lactide, dioxanone, etc. These polymeric materials do not have the dead-bend morphology of a metal and, hence, they cannot be clinched in the same manner as a metal staple. To use these polymers, the fasteners are designed as two-piece fasteners. This means one piece of the fastener is placed on one side of the tissue to be joined and the second piece of the fastener is placed on the other side of the tissue to be joined. One piece of the fastener is a U-shaped staple which has legs which are caused to penetrate the tissue. On the opposite side of the tissue is the second fastener piece or receiver which is a member used to engage the legs to interlock therewith once the legs have penetrated the tissue and, hence, join the tissue together.
As can be appreciated this major change in design and configuration of fasteners causes a number of problems. First, the fasteners must be designed to be sufficiently sharp and strong to penetrate the tissue or in certain instances some arching means must be used with the fastener to assist in penetrating the tissue. Also, the fasteners must be designed to develop an interlocking between the two pieces.
When applying these fasteners the instrument must hold the pieces until one piece has penetrated the tissue and the opposite piece is interengaged and locked on to the penetrating portion of the other member. Once this is accomplished the instrument must then release both pieces preferably simultaneously.
The instrument must be designed to firmly hold both pieces of the fasteners until the instrument is correctly positioned and the fasteners ready to be placed to join the tissue. The instrument must then uniformly and smoothly release both pieces of the fasteners as the tissue is joined. All instruments should perform these functions in an identical manner so that surgical techniques are uniform and the surgeons can rely on the instrument performing in the same manner each time they are used. Also, in view of today's emphasis on medical costs, the instrument should be economical to produce.
It is an object of the present invention to provide fasteners which are reliably held by an instrument and simply and reliably released by the instrument at an appropriate time. It is a further object of the present invention to provide a two-piece fastener that reliably aligns itself and interlocks when joining tissue. It is yet another object of the present invention to provide fasteners and instruments that are simple in construction and economical to produce.